public class MyUtil {
    public static String percentage2fivegrade(int grade) {
        if (grade < 0)
            return "错误";
        else if(grade<60){
            return "不及格";
        }
        else if(grade<70){
            return "及格";
        }
        else if(grade<80){
            return "中等";
        }
        else if (grade<90){
            return "良好";
        }
        else if (grade<=100){
            return "优秀";
        }
        else
            return "错误";
    }
}